1. Field of the Invention
The present invention relates to a calendar mechanism and a timepiece having the same.
2. Description of the Related Art
A variety of techniques are known as techniques taking a form of a so-called automatic calendar mechanism which discriminates between a long month (a month with 31 days) and a short month (a month with 30 days or less) and performs month feeding as the calendar mechanism.
In the automatic calendar mechanism, a date is fed by an amount of two days at the end of the month (30-th date) in the short month other than February, and, for it, a variety of mechanisms have been proposed (Japanese Patent No. 2651150 (Patent Reference 1) or JP-A-2005-326420 (Patent Reference 2)).
In a calendar mechanism of Japanese Patent No. 2651150 (Patent Reference 1), a month cam for discriminating a long month and a short month is used, but an elastic arm portion of the date feed finger is forced to be deformed and is fed at one tooth a day in a normal state (dates other than an end of the short month), and stability of the operation of the date feed finger is easily damaged. In addition, a Zala load (a load related to the rotation of the wheel train) is easily increased structurally, and then a loss in energy is easily increased. In addition, using the month cam itself is widely known (for example, JP-A-2009-128119 (Patent Reference 3) in addition to Japanese Patent No. 2651150 (Patent Reference 1)).
In a calendar mechanism of JP-A-2009-128119 (Patent Reference 2), an additional mechanism may be attached to a date indicator, but a helical wheel mechanism at which the number of teeth is set to operate in a predetermined manner is used, and a structure thereof may be very complicated.